Various types of valves are used to shut off and isolate a bore hole of a well from communication with the surface. Some of these valves are deployed to a depth within a bore hole and are used to shut off the well bore at the desired depth.
There are many reasons when it may become necessary to shut off a well bore below the surface. As an example, it may become desirable to close off the bore hole of an offshore well in the event of an approaching storm so as to allow personnel to evacuate. It may become desirable to perform maintenance on surface well control equipment.
Deployment of a below surface valve is desirable because most of the drill pipe being actively utilized can be left within the well bore and hung off while the drill pipe above the valve is retrieved. Once the upper part of the drill string has been retrieved, the surface well control equipment may be completely closed. This procedure expedites the time required to prepare for an evacuation because all of the drill pipe does not have to be pulled from the well bore.
Previously, deploying a downhole valve is accomplished by retrieving at least part of the drill string, then securing an anchoring device such as a packer to the upper end of the portion of the drill string still in the bore hole. The valve is secured to the upper end of the anchoring device, and a connector secures to the upper end of the valve. The operator attaches a running string or upper string to the connector and lowers the assembly to a desired depth in the well with the valve open to allow fluid to enter the upper string. Once at the desired depth, the anchoring device is activated, usually by rotation, to grip and seal to casing in the bore hole. Once the anchor is set, the operator slacks off, which transfers the weight of the drill pipe to slips of the anchor and to the casing.
At this point, the valve is normally still open and requires further manipulation to be closed. As an example, the upper string may be rotated to close the valve as well as disconnect the connector from the valve. The upper string may then be retrieved.